[LESS1]

Originally Posted by cirpower

Thank you for the good info and sharing your experience. I might look into sway bars down the road, but I feel I have to fix the brakes now first and given that Chevy changed that themselves, the rear cradle bushings.

Definitely address brakes first. Good fluid (SRF here) and stainless steel brake lines should help considerably. Cradle bushings will help but not completely eliminate what you are experiencing on the rear end. As another poster mentioned you do have a healthy amount of steering lock dialed in with heavy throttle in some of the slower corners. Which contributes to the issue. ZL1 suspension wasn't designed and engineered for the amount of grip the 3R tires provide. You have the potential to generate more speed everywhere on the track. With this extra speed your corner entry, mid corner, exit and track out points are creating more force and loads.

Typically when you go from a street tire to a good R comp or full on slick you will need stiffer springs to get the most out of the tires. This is especially true of slicks. Otherwise, you end up where you are now with a soft feeling suspension. Which is a byproduct of the extra grip, speed, force and loads previously mentioned. When you add stiffer springs it is desirable to also increase bump and rebound damping to match. Otherwise, you could possibly lose some measure of control of the springs when they cycle. This is why the ZLE package has improved Suspension, bushings and DSSV in place of MRC. Ultimately if you continue down this road you will find either springs and or ARBs will correct the soft feeling you mentioned. Don't misunderstand, I am not saying ZL1s can't go fast without improved Springs/ARB. Because that is not the case as you already know. However, you are leaving time on the table.

The objective with either Springs/ARBs is to increase roll stiffness. Springs do this on a verticle plane. Whereas with ARBs think more of a horizontal plane. During most phases of cornering the tires are under a longitudinal load, as well as others, so you can't get too crazy with ARBs. This is especially true for rear wheel drive platforms. And even more so in high HP rear drive scenarios. Running bigger ARBs will allow you to run a softer spring and still be able to achieve the roll stiffness necessary to exploit the tires to the fullest.

As I mentioned in my first post I like bigger ARBs and the softest springs possible without hitting the bump stops. This approach provides a more compliant ride which translates into the tires tracking the road irregularities better. Thus keeping the tires in contact with the road longer, providing more overall traction. Which equals better lap times provided you can take advantage of the increases. Search for "big bar soft spring" on the old interwebs and you'll find a wealth of info on this approach. Good luck with your quest and keep us posted on how you progress.

[TrackClub]

Originally Posted by LESS1

Definitely address brakes first. Good fluid (SRF here) and stainless steel brake lines should help considerably. Cradle bushings will help but not completely eliminate what you are experiencing on the rear end. As another poster mentioned you do have a healthy amount of steering lock dialed in with heavy throttle in some of the slower corners. Which contributes to the issue. ZL1 suspension wasn't designed and engineered for the amount of grip the 3R tires provide. You have the potential to generate more speed everywhere on the track. With this extra speed your corner entry, mid corner, exit and track out points are creating more force and loads.

Typically when you go from a street tire to a good R comp or full on slick you will need stiffer springs to get the most out of the tires. This is especially true of slicks. Otherwise, you end up where you are now with a soft feeling suspension. Which is a byproduct of the extra grip, speed, force and loads previously mentioned. When you add stiffer springs it is desirable to also increase bump and rebound damping to match. Otherwise, you could possibly lose some measure of control of the springs when they cycle. This is why the ZLE package has improved Suspension, bushings and DSSV in place of MRC. Ultimately if you continue down this road you will find either springs and or ARBs will correct the soft feeling you mentioned. Don't misunderstand, I am not saying ZL1s can't go fast without improved Springs/ARB. Because that is not the case as you already know. However, you are leaving time on the table.

The objective with either Springs/ARBs is to increase roll stiffness. Springs do this on a verticle plane. Whereas with ARBs think more of a horizontal plane. During most phases of cornering the tires are under a longitudinal load, as well as others, so you can't get too crazy with ARBs. This is especially true for rear wheel drive platforms. And even more so in high HP rear drive scenarios. Running bigger ARBs will allow you to run a softer spring and still be able to achieve the roll stiffness necessary to exploit the tires to the fullest.

As I mentioned in my first post I like bigger ARBs and the softest springs possible without hitting the bump stops. This approach provides a more compliant ride which translates into the tires tracking the road irregularities better. Thus keeping the tires in contact with the road longer, providing more overall traction. Which equals better lap times provided you can take advantage of the increases. Search for "big bar soft spring" on the old interwebs and you'll find a wealth of info on this approach. Good luck with your quest and keep us posted on how you progress.

Very well presented opinion, but i do have some comments.

Firstly, i think one can do no better than MRC for a dual purpose car and i fully agree that proper match between springs and dampers is absolutely key.

Secondly, sway bars are used mainly as a tool to adjust final balance F vs R.
Bigger bar up front will lead to more understeer. Bigger bar in the rear will induce oversteer. Etc.

I also think that both zl1 and ss 1le MRC based suspensions are extremely capable on any tire. Many examples of very fast laps even on full slicks on stock suspensions. The weight transfer will be a bit sped up with stickier tire, but a competent driver will manage it just fine. As results show in recorded laptimes on this forum. More often than not, folks go for a bigger F bar because they use aftermarket wheels that may change track width and hence balance (usually towards oversteer, especially with a square set up).

Race cars have stiffer springs not because they provide better grip (to the contrary), but because of big aero putting high loads on the springs. Every pro race team will run the softest spring they can get away with, as softer suspension provides most mechanical grip. At the same time, they need a stable platform to max the aero effect, including keeping the F splitter as close to the ground as posssible. If you watch Nascar stock cars with low aero on a road course, they are sprung soft for max mechanical grip. Yet they use slicks and are capable of very fast laptimes. Frankly, i could put slicks on a Camry and nothing bad would happen, except for the car turning much faster laps than on regular rubber it was engineered for. This and maybe a broken hub, or two

I also agree with your last paragraph: if somebody does desire bigger bars for some reason, match them with softest springs possible not to give up mechanical grip advantage. But i disagree, that without running a stiff bar one cannot take full advantage of softer rubber. Not on cars with excellent suspension like ss 1le and zl1 anyway, both of which have very mild aero only. What i will add however, is that a bigger bar, while dialing more understeer to an overall balance, will also speed up INITIAL transitions. That could be good if a driver is after that specifically and capable of taking advantage of it, or real bad as it could result with destroyed outside F tire rather quickly. Been there done it

Anyhow, good entertaining dialogue. Cheers!

[LESS1]

Originally Posted by TrackClub

Very well presented opinion, but i do have some comments.

Firstly, i think one can do no better than MRC for a dual purpose car and i fully agree that proper match between springs and dampers is absolutely key.

Secondly, sway bars are used mainly as a tool to adjust final balance F vs R.
Bigger bar up front will lead to more understeer. Bigger bar in the rear will induce oversteer. Etc.

I also think that both zl1 and ss 1le MRC based suspensions are extremely capable on any tire. Many examples of very fast laps even on full slicks on stock suspensions. The weight transfer will be a bit sped up with stickier tire, but a competent driver will manage it just fine. As results show in recorded laptimes on this forum. More often than not, folks go for a bigger F bar because they use aftermarket wheels that may change track width and hence balance (usually towards oversteer, especially with a square set up).

Race cars have stiffer springs not because they provide better grip (to the contrary), but because of big aero putting high loads on the springs. Every pro race team will run the softest spring they can get away with, as softer suspension provides most mechanical grip. At the same time, they need a stable platform to max the aero effect, including keeping the F splitter as close to the ground as posssible. If you watch Nascar stock cars with low aero on a road course, they are sprung soft for max mechanical grip. Yet they use slicks and are capable of very fast laptimes. Frankly, i could put slicks on a Camry and nothing bad would happen, except for the car turning much faster laps than on regular rubber it was engineered for. This and maybe a broken hub, or two

I also agree with your last paragraph: if somebody does desire bigger bars for some reason, match them with softest springs possible not to give up mechanical grip advantage. But i disagree, that without running a stiff bar one cannot take full advantage of softer rubber. Not on cars with excellent suspension like ss 1le and zl1 anyway, both of which have very mild aero only. What i will add however, is that a bigger bar, while dialing more understeer to an overall balance, will also speed up INITIAL transitions. That could be good if a driver is after that specifically and capable of taking advantage of it, or real bad as it could result with destroyed outside F tire rather quickly. Been there done it

Anyhow, good entertaining dialogue. Cheers!

Thank you for your input. In this case, aero is not a part of the equation. And this would certainly factor into spring selection if it was. MRC is very good for dual purpose. For all out performance though if it was the best solution don't you think GM/Chevy would have included with the ZLE package? Anyway the point I am trying to make is roll stiffness. Which is a factor of both springs and ARBs. Most folks, yourself include it would seem like to think ARBs are used exclusively to dial in that finite O/U steer balance. And this is not wrong. However, ARBs can also be used as I have described in my previous response to the OP. Stiffer springs will as you know increase the force need to cycle (along with damper) and contribute to roll stiffness. Too much spring can and will create an O/U steer condition, just like too much ARB. The difference here is ARBs will have less impact on other suspension dynamics. Compared to springs which are too stiff. The same is true if both are too soft.

This is not a new concept and is one I have used in a past life on a few cars very successfully. For now, my SS 1LE is stock, I want to see how fast I can go before changing stuff out. When that time does come bigger ARBs are near the top of my to do list. Along with an aftermarket body control module to dial in bump/rebound to compensate for new ARBs. Ultimately either approach works, I just happen to favor "BBSS" over stiffer springs.

[LESS1]

Originally Posted by TrackClub

I also think that both zl1 and ss 1le MRC based suspensions are extremely capable on any tire. Many examples of very fast laps even on full slicks on stock suspensions. The weight transfer will be a bit sped up with stickier tire, but a competent driver will manage it just fine.

I forgot to add. The above is true for OEM setup to a point. I'll come back to this in a min. The fast laps you mentioned are a mix of totally OEM trim (- Chevy Track alignment) and folks on 19" wheels with either OEM or aftermarket tires. The folks on 19" wheels have an advantage whether they are on an OEM tire or not. The ~20lbs to 40lbs dropped in wheel weight is massive and contributes not only to improved suspension motion and compliance, improved turn in, acceleration as well as braking. Additionally, this also adds equivalent horsepower due to the reduced rotating inertia weight, figure ~.428HP per pound removed. So for me, this change is not viewed as insignificant.

Circling back to my opening comment regarding OEM setup. This is true or at least it was for me when you are first learning the car and the limits. During this time period, everything is tight and stiff, hardly any body roll noticed, seats are awesome and hold you in tight. Then as you progress and add speed, you start to notice the body roll and wish you had more roll resistance so you could get the car to hold the line you want during a quick transition so you can get back to the throttle sooner.

Add more speed and you notice you are using your knees to hold yourself in place because the seats aren't cutting it. Toss in a good R comp or slick and this issue becomes even worse, not to mention the soft suspension problem! My point is this is all relative to the skill and experience of the throttle jockey wheeling the car. Some will never experience this on an OEM setup and it will seem foreign the idea that SS 1LE as delivered could be anything but stellar at all times. Push very hard and you do begin to notice where Chevy made compromises. I fully understand the rationale behind these decisions as most will never exploit the car's performance to experience this on the OEM tire. Again "on the OEM tire". For clarity, I am not saying as delivered SS 1LE is not an All-Star punching well above its price and class because it certainly does. Push very hard though and there are areas needing improvement if you want to go even faster.

[TrackClub]

Thanks for your additional thoughts.

I am aware of ARBs affecting roll stiffness.
I am just not sharing the opinion that they are absolutely required to get value out of softer tires, including slicks.

I too had prior cars, modded beyond street legal, etc.
I don't disagree, that if somebody wants to get every tenth out of the platform, then mods are in order.
Power, weight and driver (mods) usually produce the best results, as one very famous pro once said
But of course suspension plays a role too, but much depends on what one is swapping from quality wise.

By and large i agree with everything you say, incl I'd go with stiffer ARBs before stiffer springs on a non aero car, etc. Obviously you have experience here and it all makes sense.

At the same time, ZLE does have aero, so stiffer suspension is more justified perhaps. It is also a marketing tool imo, as was the case with Z/28. For 50% more $ over ZL1, $75k that is, back in a Gen5 time. Much was written about its trick Multimatic DSSV suspension, souped up LS7, sticky Trofeo Rs, gutted interior, etc.
Then Gen 6 SS 1LE cames around, with less power, less sticky tires, bigger and heavier wheels, MRC and it beats it around Laguna for half the price. Miracle, or magic?

Sure, less rotating mass, better gearing, etc will all have a positive effect assuming a driver can get the most out of the car. But the biggest difference will be stickier rubber by far. So, i am not discounting every little bit producing a positive effect, but some mods produce 2% of benefit (which would take Hamilton to take advantage of) while others produce 20% (which pretty much everyone will get *some* benefit from).

Ive driven my car for 3 yrs now for about 60 days at 7 different venues. Tried 3 different tires. 3 different brake pads. Went back to stock. The only thing i wish for is an extra 100hp. But even stock, if someone can drive to close to its limit, it is an amazing track car, capable of embarrassing cars that cost 2 or even 3 times more. That's good enough for me. But others may disagree and that's fine

Many put 18 rims and slicks changing nothing else on this platform.

Many have no idea how fast stock 1le is in very capable hands and start modding the car before they find out.

Some even surprise themselves after having run uber tires for 3 years, then going stock (look up Fastest Laps for NCM and post #771).

But, i agree: if i wanted my car to be even faster, I'd put it on a diet, increase its power, put slicks on and due to different ETs for smaller wheels, which affect track width and hence balance, get adjustable ARBs. But only if i felt the need for them. But then the car would lose the warranty and that's one of the reasons i bought it for.
Not only this, but if i ever decided to go back to building a track car I'd buy a cheap C5 and spend some cash. Much better platform to start from to arrive at sub 3000lb 600hp end point.

PS i had a full 5 points, etc before and i still had sore knees And many pros wear knee pads in full on race cars. Funny, and perhaps i use Recaros differently, but i am yet to suffer rubbed off skin in my 1LE. And i do push it pretty good.

Enjoying the dialogue! Cheers!

[TheRealJA105]

Agree with you both, as I have BMR adjustable sway bars already on my car with stock springs and sticky tires are by far the best car mod at the track.

[cirpower]

Thanks everyone for the great perspective and highly interesting discussion. I agree, the car is so extremely capable right out of the box that really no mods are needed. After all, pretty sure I will not become an Indycar racer anymore .

I do have a plan to work on for the next event at the end of June:

- check alignment
- bleed brakes and ABS module
- if front pads are worn, replace with slightly more aggressive pad

...then drive the wheels off the car.

Note: I could not yet find anyone that is capable/willing to do an ABS brake bleed through the GM scan tool....

[TrackClub]

Originally Posted by TheRealJA105

Agree with you both, as I have BMR adjustable sway bars already on my car with stock springs and sticky tires are by far the best car mod at the track.

[TrackClub]

Originally Posted by cirpower

Thanks everyone for the great perspective and highly interesting discussion. I agree, the car is so extremely capable right out of the box that really no mods are needed. After all, pretty sure I will not become an Indycar racer anymore .

I do have a plan to work on for the next event at the end of June:

- check alignment
- bleed brakes and ABS module
- if front pads are worn, replace with slightly more aggressive pad

...then drive the wheels off the car.

Note: I could not yet find anyone that is capable/willing to do an ABS brake bleed through the GM scan tool....

Sounds like a good plan And if ya hit 45s maybe IndyCar will call afterall lol!

Id just flush the fluid and put SRF in. Dont know how you did the first flush, but it is easy to get air in the system if not done properly. I do mine with my mechanic as a 2 person job...never had to bleed ABS yet.

[cirpower]

Originally Posted by TrackClub

Sounds like a good plan And if ya hit 45s maybe IndyCar will call afterall lol!

Id just flush the fluid and put SRF in. Dont know how you did the first flush, but it is easy to get air in the system if not done properly. I do mine with my mechanic as a 2 person job...never had to bleed ABS yet.

you want to pass them my number?

I did a complete flush using Motul 600 with the Motive bleeder before the last event.

I forgot the most important for the next event: Driver mod, learn from all the feedback here and analyzing the drive.

[TrackClub]

Originally Posted by cirpower

you want to pass them my number?

I did a complete flush using Motul 600 with the Motive bleeder before the last event.

I forgot the most important for the next event: Driver mod, learn from all the feedback here and analyzing the drive.

They would be delighted to see ya, i am sure. But that would be one long drive for you
Ive read mixed reviews on the 600. But never tried it myself, so cant offer anything objective.
Ya, the nut behind the wheel is never screwed on tight enough

[cirpower]

Update, I removed the wheels and bled the brakes this evening:

- the inside of the tires is barely worn, now I think they could do with a little bit more camber (definitely more use on outside than inside of tire)
- overall tires still look like new
- very little air (one tiny bubble front right) in the calipers
- brake pads still in very good shape, no need to change

Also, here is some PDR information of the run in the youtube movie:

Max speed 142.7mph
Max lateral G 1.33

Max tire temp LF 169 / LR 142 / RF 190 / RR 156
Max tire pressure LF 35.4 / LR 35.4 / RF 35.4 / RR 34.8

Max water temp 228
Max engine oil temp 280
Max transmission temp 243

Max boost 12.3

Updated plan after inspection:
- check alignment and if necessary adjust to track specs
- see if pedal is still soft, if yes, switch to SRF

cheers
cirpower

[cirpower]

Note: Looking at the tire temps it doesn't surprise me that people are wearing the fronts faster than the rears.

[TrackClub]

Originally Posted by cirpower

Note: Looking at the tire temps it doesn't surprise me that people are wearing the fronts faster than the rears.

The fronts will always wear out faster except for when at the strip, which is a reverse

May i suggest a slight change of plan please:

1. Do put track alignment in (it will make the car handle better!!!)
2. Do put SRF in (the best, only 1 bleed mid season then fresh at start of next season. Easy peasy. It works!)

Apologies in advance for being pushy Cheers!